(1) Field of the Invention
This invention relates to a substrate treating system for treating semiconductor substrates, glass substrates for liquid crystal displays, glass substrates for photomasks, substrates for optical disks and so on (hereinafter called simply “substrates”). The treating system is constructed to expose substrates having resist film formed thereon, coat the substrates with the resist film before the exposing process, and/or develop the substrates after the exposing process.
(2) Description of the Related Art
The general flow of a lithographic process is divided roughly into (1) resist coating, (2) exposure, (3) post-exposure bake (hereinafter referred to as “PEB” where appropriate), (4) development, (5) etching, and (6) resist removal. The reaction of resist film on exposed portions starting in the step of (2) exposure continues through the step of (3) PEB, and stops when substrates are subjected to a cooling step. Thus, in the lithographic process, the steps of (2) exposure and (3) PEB, and the cooling step associated therewith need to be carried out at a stretch and cannot be separated in time.
Further, to cope with an increasingly refined linewidth of patterns, there are methods in which exposure is done twice in different patterns using two types of masks (in what is called double exposure). In one method, for example, one of the masks is used for a vertical pattern, and the other mask for a horizontal pattern. In another method, patterns are exposed such that, between patterns projected through one of the masks, a pattern according to the other mask is located. A lithographic process for such double exposure is carried out in a procedure of repeating only (2) exposure twice in succession, or in a procedure of repeating twice a plurality of steps from (1) resist coating to (6) resist removal, for example.
FIG. 1 shows an outline of a conventional apparatus that carries out treatments from (1) resist coating to (4) development noted above. This substrate treating apparatus includes an indexer block 81, a resist block 83, a developing block 85, an interface block 87 and an exposing machine 89, which are connected in-line. Each of the resist block 83 and developing block 85 has heating units HP and cooling units CP, besides resist coating units SC or developing units SD, for heat-treating wafers W as appropriate in the course of resist coating or development. The heating units HP of the developing block 85 are used in the treatment for (3) PEB noted above. The respective blocks 81, 83 and 85 have transport mechanisms 91, 93 and 95 for transporting wafers W. The interface block 87 also has a transport mechanism not shown.
In the substrate treating apparatus constructed in this way, a wafer W is first fed from the indexer block 81 to the resist block 83, and loaded into one of the resist coating units SC. After resist film is formed on the wafer W, the wafer W is transported to the exposing machine 89. The wafer W having been exposed is transported to the developing block 85. In the developing block 85, the wafer W is loaded into a heating unit HP, cooling unit CP and developing unit SD for PEB in the stated order. The wafer W undergoes predetermined treatment in each of these units HP, CP and SD. After the treatment in the developing block 85, the wafer W is transported back to the indexer block 81. The transport mechanism 91 deposits the wafer W having undergone the series of treatments in a storage container C (as disclosed, for example, in Japanese Unexamined Patent Publications No. 2003-324139 and H11-154637).
However, the following drawback is encountered when the conventional apparatus carries out a lithographic process for double exposure, and especially when exposure is done twice in succession in the step of (2) exposure. The time taken by the exposing machine 89 in exposing each substrate becomes approximately twice as long, and the extended processing time of the exposing machine 89 has an adverse influence of lowering the operating rates of the resist block 83 and developing block 85.